By logo this topic means Spash Screen.
I agree with you, the jME3 logo is the monkey itself, like the favicon of this page.
Logo:
http://hub.jmonkeyengine.org/uploads/default/1439/87eeb25a7db82bd4.png
Banner:
http://hub.jmonkeyengine.org/uploads/default/1252/91fcc91347189c84.png
Splash Screen:
http://jme-hub-cdn.jmonkeyengineor.netdna-cdn.com/uploads/default/optimized/2X/4/47cfcbedfb1be1ca15402706eed77c2410ae6ab9_1_690x303.png